Congratulations!, you're furnace is pretty close to the right size. You have experience exactly how a HVC systm is supposed to operate. Sadly few get to expereince this. Actually in your location, it's probably still a little big, but 60k is the smallest Infinity furnace they make. Based on your observations, a 45k would have been large enough. If it was perfectly sized, it would be on high stage most of hte time in thsoe conditions. But your at least close.